<!--
 * @Descripttion: 
 * @version: 
 * @Author: Ansel
 * @Date: 2020-05-08 17:15:45
 * @LastEditors: Ansel
 * @LastEditTime: 2020-05-08 17:33:29
 -->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content=
    "width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .demo{
            position:fixed;
            width: 100%;
            height: 100%;
            left: 0;
            top: 0;
            border: 1px solid black;
        }
    </style>
</head>
<body>
    <div class="demo">

    </div>
</body>
</html>